1. Field of the Invention
The present invention relates to a method and apparatus for the melting of materials to be treated. More specifically, the invention relates to an apparatus that comprises a container in which melting is performed, thus enabling a one-step disposal method for the treated materials.
2. Description of the Prior Art
The use of vitrification methods for safely disposing contaminated soil or waste materials (hereinafter referred to as material to be treated) is known in the art. Examples of such methods are provided in U.S. Pat. Nos. 4,376,598; 5,024,556; 5,536,114; 5,443,618; and, U.S. RE Pat. No. 35,782. The disclosures of these patents are incorporated herein by reference.
Generally, the known vitrification methods involve placement of the material to be treated into a vitrification chamber or vessel. Electrodes are then introduced into the material and a high current is supplied there between. Application of the current is continued until the temperature of the material is raised to the point where the material begins to melt and is continued until the material is completely melted. If certain cases, other additives may be required to provide an initial electrically conductive resistance path through the material to be treated if such material is not capable of adequate current conduction. Once the resistance path is initiated and melting of the material begins, the molten material itself will continue current conduction.
In the course of melting the material, organic components are destroyed or vaporized and the gases are normally vented through a suitable scrubber, quencher, filter or other known device or method.
Once the material is sufficiently melted and all organic components are treated, the electricity supply is terminated and the molten material allowed to cool. The cooling step then results in a vitrified and/or crystallized solid material. In this manner, inorganic contaminants are immobilized within a solid, vitrified mass thereby ensuring containment of the contaminants and facilitating disposal of same.
In the known methods, vitrification is accomplished within a complex refractory-lined melting apparatus or within a pit dug into the soil. In U.S. Pat. No. 5,443,618, an example is provided of a vitrification apparatus comprising a chamber that is either permanently in place (as in a treatment facility) or one which can be dismantled and reassembled at desired locations. In each case, the molten mass is removed from the chamber and processed further separately. Such further processing may involve burial, or other type of disposal, of the vitrified and/or crystalline mass. The apparatus known in the art for conducting vitrification process are normally complex structures including various electrical supply systems, waste feed systems, molten glass discharge systems, cooling systems and venting systems. Such systems require the removal of the melted mass while in the molten state, hence requiring the above mentioned molten glass discharge systems. In these cases, the melt is either poured or flowed out as a molten liquid into a receiving container.
In U.S. Pat. No. 4,376,598 and U.S. RE Pat. No. 35,782, vitrification processes within a pit are described. In this case, the material to be treated is dumped into a pit or trench in the ground and a soil or other type of cap is placed as a cover. Electrodes are then introduced to conduct the vitrification process as described above. Once the process is completed, the vitrified and/or crystalline mass is left buried in the ground. As will be appreciated, certain contaminants such as radioactive waste etc. cannot safely be disposed in this manner as they must be disposed of in regulated burial locations.
Generally, the known methods are expensive and are used in difficult situations to which there is no alternative. Therefore, there exists a need for a vitrification apparatus and method that overcomes various deficiencies in the prior art.